One of important requisites for a next generation wireless access system is to support a high data rate requirement. To this end, many ongoing efforts are made to research and develop various technologies including MIMO (multiple input multiple output), CoMP (cooperative multiple point transmission), Relay and the like.
In a wireless access system of a related art, a single carrier is mainly considered despite setting bandwidths of uplink and downlink to differ from each other. For instance, a wireless communication is provided based on a single carrier as follows. First of all, the number of carriers) configuring each of the uplink and the downlink is 1. Secondly a bandwidth of the uplink and a bandwidth of the downlink are symmetric to each other.
Yet, considering that frequency resources are almost saturated, as a method of securing a wideband bandwidth to meet a higher data rate requirement, basic requirements for enabling scattered bands to respectively operate independent systems are designed to be met and CA (carrier aggregation/multiple cells) in concept of bundling a plurality of bands into a single system is introduced.
In this case, a carrier of a bandwidth unit capable of each independent operation can be named a component carrier (C). In order to support an increasing transmission capacity, the recent 3GPP LTE-A or 802.16m continues to extend its bandwidth up to 20 MHz or higher. In doing so, at least one or more component carriers are aggregated to support a wideband. For instance, if a single component carrier supports a bandwidth of 5 MHz, 10 MHz or 20 MHz, it is able to support a system bandwidth up to maximum 100 MHz in a manner of bundling maximum 5 components.
However, in case that a user equipment reports a channel state information (CSI) on each carrier at a same timing point in a wireless access system supportive of carrier aggregation environment, it may cause a problem that a base station may perform an erroneous decoding on the received channel state information or perform blinding decoding several times.